9100 with release of native Twitter (BES administration of course)
BES Infrastructure - entire ecosystem enhancements; including Novel support in v5, and hopefully remote control.
HSPA for faster data rates.
OS highlights: Webkit and Flash integrated making or much faster os/apps/etc.
Screw widgets (in the traditional sense); they consume so much data I might as well just goto the website. With Flash coming to the OS then you'll see a powerful and useful widget.
Lastly I'd like to see html5 support in the webkit engine. Boxtone will no doubt have an improved solution.